Agriculture Reference
In-Depth Information
mating behaviors. Moth pheromones are complex blends of several
volatile oils. Male moths demonstrate a partial response to any moth
blend, but require the precise, species-specific blend to stimulate the full
sequence of mating behaviors. The first commercial application of man-
ufactured codling moth pheromones was in monitoring traps, replacing
the caged females. Scientists and pest-control advisors had to determine
how much pheromone to put in each trap and how long it would last in
orchards. They had to determine where to best place the product in the
orchard. Most PCAs hang pheromone traps at the height of a pickup
truck's window, but they should be placed high in the tree.
The codling moth populations in the Sacramento River pear district
and the apple growing regions of Washington State began to develop
resistance to azinphosmethyl, about the time a biological pesticide com-
pany released the first synthetic pheromone dispenser. In the laboratory,
Isomate twist ties worked well on individual males, but because they are
based on modifying collective behavior rather than killing the insect,
scientists could not draw valid inference from their performance in test
plots. The pesticide-resistance crisis provided an opportunity for scien-
tists to study codling moth pheromone mating disruption on a field scale.
Scientists and PCAs were able to draw some from their understanding of
how pheromones stimulated insect behavior, but they had much to learn
about how to manage an orchard flooded with pheromones. The volume
and concentration of pheromones in Doug Hemly's orchard was without
precedent in evolutionary history, and it was studied intensively.
Scientists developed several products to confuse the male codling
moth. They found ways to put sex pheromones in plastic tubes, aerosol
cartridges, wax flakes, chopped fibers, and microencapsulated oils. The
twist ties worked best when hung in the upper third of the canopy. Harry
Shorey of UC Riverside modified a bathroom deodorizer to create an
aerosol device to release pheromone clouds (figure 6.1). These “puffers”
were more expensive, but could be placed more widely in an orchard.
They are less effective when orchards have high edge-to-area ratios.
Puffer failures were quite costly, and later versions were controlled by
computer chips to verify operation and release pheromones only during
the twilight hours when the females call their mates. Pear trees are now
pruned to a height of about 15 feet to reduce workplace liability for farm
laborers on ladders. This results in a more compact orchard volume, and
